Indexable cutting tools with a cutting insert attached to a holder may be used as a cutting tool used in a cutting process or the like. The cutting insert used for the cutting tool may include a polygonal-shaped upper surface, a side surface, and a cutting edge located at an intersecting part of the upper surface and the side surface. The above cutting tool may be capable of cutting out a workpiece by bringing the cutting edge into contact with the workpiece.
Patent Document 1 (Japanese Unexamined Patent Publication No. 2003-220503) discloses a cutting insert used for the above cutting tool. The cutting insert discussed in Patent Document 1 may include a flat surface on a rhombus-shaped upper surface. The flat surface may be projected than a cutting edge and arranged highest in a thickness direction. The flat surface may extend toward a midpoint of a side ridge part of the rhombus shape. The cutting insert discussed in Patent Document 1 may further include breakers on the upper surface which are respectively formed at an acute angle corner and an obtuse angle corner. A top portion of each of the breakers may be a flat surface located at a height equal to the flat surface described above. The flat surface and the top portions of the breakers may function as a seating surface.
The flat surface serving as a seating surface may be arranged toward the midpoint of the side edge part serving as the cutting edge in the cutting insert discussed in Patent Document 1. Thus, the cutting insert discussed in Patent Document 1 may have seating stability. However, chip disposal may be unstable when used in a cutting process, such as a chamfering process.